With the advent of digital television transition standards a better means for interconnecting digital multimedia devices such as set top boxes, DVD players, and the like to digital televisions became needed. Digital televisions, such as high-definition televisions, typically produce high quality picture resolutions. For example, high-definition televisions may have resolutions greater than that of televisions conforming to the North American Standard Television System, which has a typical resolution of 720 pixels per 483 lines.
The use of analog connections to connect devices to digital televisions, such as high-definition televisions, introduces losses that can affect picture quality. Furthermore, analog connections require the digital signal to be converted to an analog signal and then back into a digital signal. Digital connections maintain the high quality picture resolutions of digital content and eliminate the need for digital to analog and analog to digital signal conversion.
One digital connection standard that has come to the forefront of digital connections is the high-definition multimedia interface (HDMI). HDMI provides the benefits of an all digital interface that minimizes the number of cables needed for carrying audio and video signals from a source to a monitor, for example. As the number of devices available to connect to a digital monitor, such as a high definition television, increases, there arises a need to have all HDMI devices connected at the same time. This helps avoid removing one source cable to play another source. Examples of HDMI devices may include a digital video disc (DVD) player, a digital video recorder (DVR), a set top box, or video game system. Digital video monitoring devices such as high definition televisions typically have a limited number of HDMI inputs. Typically, a digital video monitoring device has only one or two HDMI inputs. Therefore, if one has more than one or two HDMI sources, the sources must be disconnected and reconnected as use of an HDMI device is used.
One solution to the problem is the use of an HDMI switch. An HDMI switch provides the ability to select from several inputs that is then connected to a single output or multiple outputs that may be connected to an HDMI sink, such as high definition television. Such a switch provides the user the convenience of having many HDMI devices connected to a device that has a limited number of inputs, such as a digital video monitor. One drawback to such a device is that to access one of the multiple sources connected to an HDMI switch the user must manually select the source on the HDMI switch to output that source from the HDMI switch. To select the appropriate source or input device to be outputted on the HDMI switch, the user must know exactly which source is connected to which input. Furthermore, when the HDMI switch is first turned on the user must manually select the input of a device connected to the input that is on in order to deliver that input to the output or outputs of the HDMI switch. As above, this requires the user to know exactly which input source device is connected and to select the input switch on the HDMI switch to have that input source available to the output or outputs of the HDMI switch.
Current HDMI switches that automatically detect a source do so based on availability of a power voltage present on the input, such as the presence of the positive 5 volts power signal. Once the HDMI switch detects the presence of the positive five volt power on the input, the HDMI switch selects that input as the source to be provided to the output or multiple outputs on the HDMI switch. The problem with this automatic selection scheme is that many source devices constantly produce a positive five volts on the input even when no video signal is transmitted. For example, many source devices produce a positive 5 volts power signal when in a standby mode without producing any other signals such as video. Alternatively, some source devices produce a positive 5 volts power signal and a video signal (such as a logo screen) in a standby mode. This leads to the problem of an HDMI switch automatically selecting an input that is not actually producing any valid output, such as a video signal that a viewer would want to watch.